Concentric line



June ll, 1940.

Filed Aug. 31, 1958 a ttorneg Patented June 11, 1940 UNITED STATES i PATENT OFFICE CONCENTRIC LINE- Lester John Wolf, Audubon, N. JL, assignor to Radio Corporation of America, a corporation of lil able contact of the requisite low impedance and resistance. The problem is especially difficult when the contact to be adjusted is at the closed end of a concentric line, at which point the current is maximum. Poor Contacts not only attenuate the high frequency currents but tend to introduce microphonic disturbances into the system and to change its tuning especially when the apparatus is subject to mechanical vibration or to variations in the intensity of the currents being transmitted.

Accordingly, the principal object of thepresent invention is to provide a mechanically movable but nevertheless extremely low resistance contact for use between parts of a tuned circuit such, for example, as the outer and inner conductors of a concentric line.

Another object of the invention is to provide a readily adjustable and trouble-free terminal or shorting plug" for altering the efiective length (and hence the tuning) of a concentric line.

Other objects and advantages together with certain details of Construction will be apparent and the invention itself will be best understood by reference to the following specification and to the accompanying drawing, wherein:

Figure 1 is a longitudinal sectonal view of a concentric line with the shorting plug of the invention in position,

Figure 2 is an end elevational View of the shorting plug of Fig. 1,

Figure 3 is a sectional elevation taken on the line 3/3 of Fig. 2, and

Figure 4 is an exploded View of the several different parts of the shorting plug of Figs. 1 to 3 inclusive.

Like reference characters designate the same or corresponding parts in all figures.

In Fig. 1, A designates the outer and B the inner conductor of a concentric line. A shorting plug indicated generally at C` is movable within the outer conductor, and constitutes a conductive connection between conductors- A and B. Move- 1938, Serial No. .227,795

I (Cl. 178-44) ment of the shorting plug C along the surfaces of the inner and outer conductors alters the effective length and hence the tuning of the apparatus. As will hereinafter more fully appear, such movement may be achieved by manipulating 5 a plurality of insulating rods or handles D which extend from the shorting plug beyond an open terminal of the outer conductor B.

Considered in its entirety, the shcrting plug C may be said to` comprise an annulus having an outside diameter corresponding substantially to the inside diameter of the outer conductor A and an inside diameter corresponding substantially to the outside diameter of the inner conductor B.

This shorting plug C is constituted essentially of an inner split ring i (the inner surface of which comprises the inner peripheral surface of the annulus), an outer split ring 3 (the outer surface of which comprises the outer peripheral surface of the annulus) and two split discs 2 and 4 respectively (the exposed faces of which comprise the major surfaces of the annulus) which are arranged in spaced parallel relation and span the space between the inner and outer rings I and 3. Each of the split rings l and 3 and split discs 2 and 4 are preferably constituted of three segments each of which extends substantially 120 around a central axis a-a which corresponds to the common axis of the concentrc conductors A and B.

As shown more clearly in Figs. 3 and 4, the outer or concealed surface of the inner split ring l co mprises two surface sections la and lb` which are each beveled or inclined inwardly (i. e., toward the axis a-a) from a protruding ridge or rim Ic which bisects the thickness dimension of the said ring. Similarly, the inner or concealed surface of the outer split ring 3 'comprises two surface sections 3a and 31) which are each beveled or inclined outwarclly (i. e., away from the central axis a-dl from a protruding ridge or rim 3c which bsects the thickness dimension of the said outer ring. The inner Za, da and outer 21), db peripheral surfaces of the split discs 2 and 4 comprise beveled surfaces which are complements of the beveled ring surfaces which are adjacent thereto. The discrete parts of these spaced discs 2 and 4 are preferably in register one with another. Tapped screw holes h in one of the registered parts of the discs accommodate screws T which, when turned by the application of a rotating force to the insulating handles D, regulate the spacing between the discs. The registered parts of thediscs 2 and 4 in being screwed toward each other exert a contracting force upon the inner ring l and an expandng force upon the outer ring 3. These oppositely directed forces are, of course, applied to the rings i and 3 through their beveled surfaces la, lb, 3c, 3b which, as previously described, are presented to the beveled peripheral surfaces Za, Zb, da, db of the discs 2 and 4.

The outer surface of the outer ring 3 is provided with a circumferential groove or recess 3g within which a coil spring S is seated. The expanding force applied to outer ring 3 is thus exerted against the inwardly directed biasing force of the spring S. When the expanding force is removed from the outer ring 3 (i. e., when the screws T are turned in the direction required to provide an increased spacing between the discs 2 and 4) the spring S urges the several parts of the ring 3 inwardly thereby contracting it. Sinilarly, as the contracting force is removed from the inner ring I (by increasing the separation between the discs 2 and 4) the adjacent surfaces of the conductor A and ring i are no longer clamped to each other, so that the entire shorting plug C (Fig. 1) may be moved by means of the insulating rods D to the exact position required to tune the transmission line.

Obvicusly, the clamping force applied to the inner and outer conductors A, B through the shorting plug C should be substantially no greater than that required to achieve an intimate mechanical and low resistance electrical connection. The thickness of the circumferential ridges !C and 3C on the inner and outer rings l and 3 will ordinarily be so chosen as to limit the intensity of the clamping force exerted upon the inner and outer conductors A and B by these rngs.

Other modifications of the invention will suggest themselves to those skilled in the art. It is to be understood therefore that the foregoing is to be interpreted as illustrative and not in a limiting sense except as required by the prior art and by the spirit of the appended claims.

What is claimed is:

i. A shorting plug for a transmission line of the type having concentric inner and outer conductors, said plug comprising a plurality of relatively movable parts constituting inner and outer surfaces each adapted to engage one of the opposed surfaces of said inner and outer conductors, spring means biased to maintain a fit between said parts, and means for contracting the inner and expanding the outer surfaces of said plug against the biasing force of said spring.

2. A shorting plug for a transmission line of the type having concentric inner and outer conductors, said plug comprising a split ring adapted to embrace the inner conductor, a second split ring adapted to be received within the outer conductor, a split disc for maintaining said split rings in spaced relation, and means for varying the spacing between the parts of said split disc whereby a contracting force may be applied to one and an expanding force to the other of said split rings as determined by the direction of change in the spacing of the parts constituting said split disc.

3. A shorting plug for a transmission line of the type having concentric inner and outer conductors, said plug comprising a split ring having an inner surface adapted to embrace the inner conductor and an outer surface which is beveled along the axis of said conductors, a second split ring having an outer surface adapted to contact the inner surface of said conductor and an inner surface beveled along said axis, the beveled surface of said inner and outer rings being inclined in the opposite direction, with respect to said axis, a split annulus mounted between said inner and outer rings and having beveled inner and outer peripheral surfaces comp1ementary respectively to the outer and inner beveled surfaces of said inner and outer split rings, and means for moving the parts of said split ring along said common axis whereby a contracting force is applied to one and an expanding force is applied to the other of said split rings through their respective beveled surfaces as determined by the direction of axial movement of the parts constituting said split disc.

LESTER JOHN WOLF. 

